1. Field of Invention
The present invention relates to a protection circuit with transistors. More particularly, the present invention relates to a display apparatus current discharging method and a display apparatus current leakage reducing method.
2. Description of Related Art
Flat panel displays are mostly made of insulating glass substrates, where electrostatic discharge (ESD) is easily induced to damage components thereof, greatly decreasing the manufacturing yield of the flat panel displays. Typically, protection circuits for preventing ESD are configured on display panels to achieve the protection of components.
FIG. 1 is a schematic view of a flat panel display with conventional protection circuits. As illustrated in FIG. 1, a display panel 100 has a plurality of scan lines 102 and a plurality of data lines 104. A plurality of display units 106 are provided at intersections of the scan lines 102 and the data lines 104. Protection circuits 112 are electrically connected between a discharging line 110 and one of the scan lines 102 or the data lines 104. When a discharging pulse is generated on the scan line 102 or the data line 104 due to the ESD of the display panel 100, the protection circuits 112 can disperse the discharging pulse to the discharging line 110 and thus prevent the display units 106 or other components from being damaged by the discharging pulse.
For the protection circuits, particularly the protection circuits for ESD used in the flat panel displays, the prior art provides several different implementations. FIG. 2A is a schematic view of a conventional protection circuit. As illustrated in FIG. 2A, two transistors 222a and 224a are electrically connected in parallel between the scan line 102 and the discharging line 110. When a drain and a gate of the transistor are short-circuited, the transistor is equivalent to a diode. FIG. 2B is an equivalent circuit diagram of the protection circuit 112a of FIG. 2A. The two equivalent diodes 222b and 224b are opposite to each other, and therefore are able to deal with discharging currents either from the scan line 102 to the discharging line 110 or from the discharging line 110 to the scan line 102.
U.S. Pat. No. 5,744,837 discloses another protection circuit, as illustrated in FIG. 3A. A protection circuit 112b comprises four transistors 322a, 324a, 326a and 328a electrically connected between the scan line 102 and the discharging line 110. A drain and a gate of each of the transistors 322a, 324a, 326a and 328a are individually short-circuited. FIG. 3B is an equivalent circuit diagram of the protection circuit 112b of FIG. 3A. The equivalent diodes 322b and 324b are opposite to the equivalent diodes 326b and 328b, and therefore, they are able to deal with discharging currents either from the scan line 102 to the discharging line 110 or from the discharging line 110 to the scan line 102.
U.S. Pat. No. 5,606,340 discloses another protection circuit, as illustrated in FIG. 4A. A protection circuit 112c comprises four transistors 422a, 424a, 426a and 428a electrically connected between the scan line 102 and the discharging line 110. A drain and a gate of each of the transistors 422a, 424a, 426a and 428a are individually short-circuited. FIG. 4B is an equivalent circuit diagram of the protection circuit 112c of FIG. 4A. As illustrated in FIG. 4B, the transistors 422a and 424a are equivalent to a switching element 422b, and ON/OFF states of the switching element 422b are controlled by the equivalent diodes 426b and 428b. When a potential difference between the scan line 102 and the discharging line 110 is great enough, the diodes 426b and 428b switch on the switching element 422b, such that the discharging currents are dispersed to the scan line 102 or the discharging line 110, which has a lower potential via the switching element 422b (i.e. the transistors 422a and 424a).
However, the foregoing conventional protection circuits have drawbacks such as large leakage currents, small discharging currents, slow discharging speed and easy disablements due to being damaged during manufacturing. In the flat panel display, a larger size or higher resolution indicates that the quantity of the contained scan lines and data lines are greater. If the leakage current of each protection circuit electrically connected to the corresponding scan line and data line is large, the total leakage current of the whole display panel becomes serious and causes tremendous power consumption. The power stored in a portable electronic device is finite. For example, the operating voltages of the in-plane switching (IPS) mode used in liquid crystal displays (LCDs) are higher than for average devices, so the leakage currents thereof are greater. In conclusion, these drawbacks are very disadvantageous to portable electronic devices and the IPS modes often used in LCD TVs.